Pyrrolidone-2-hydrotribromide

An alternative procedure to bromine itself is the use of complexed derivatives such as 2-pyrrolidone hydrotribromide (PHT), which is easier to handle. This reagent has been shown to brominate flavanones in THF, while the more vigorous conditions of hot DMSO result in concommitant dehydrohalogenation to give the flavone (Scheme 2). ... 

Pyrrolidone hydrotribromide as reagent 9,608 suppl. 29 A -Pyrroline ring, 5-hydroxy-29, 691... 

Bhaskar and Mander used the Cp2TiCl-promoted opening of epoxide 6 in the presence of pyrrolidone hydrotribromide to obtain a-bromoaldehyde 7, a crucial intermediate in the synthesis of the biologically potent gibberelhn GA32 (Scheme 16) [94],... 

The synthesis of clavine derivatives substituted in the C-14 position was described by Benes and Beran (1989). A mixture of 1-ferf-butyl-, -0-d -tert-butyl-, 2, 13-di-tert-butyl- and 2, 14-di-fert-butyl-elymoclavine resulted from the reaction of elymoclavine with tert-butylalcohol and trifluoroacetic anhydride. Sauer et al. (1990) prepared 13, 14-dibromo derivatives by bromination of 2-methyl-ergolines by different bromination reagents (bromine, pyridinehydrotribromide, pyrrolidone-hydrotribromide) in trifluoroacetic acid. When only one equivalent of bromine was used, 13-bromo derivative was preferentially formed. 

Bromination of 2 with pyrrolidone-(2)-hydrotribromide (PHT) does not produce any traces of compound 4, even in the presence of chloride ion, however other side reaction can be observed. Just a small excess of PHT produces the higher brominated compounds 5 and fi ... 

Bromination. This perbromide is useful for selective bromination of a ketone in the presence of a double bond (c/. pyrrolidone-2-hydrotribromide, 3, 240-241). In three cases reported yields are in the range 60-80%. Of course, this reagent can also be used for a-bromination of saturated ketones. No reaction was observed with camphor, however, or with esters. The intermediate monobromide formulated above in the preparation of (1) is formed on brominations with (1). In effect, the perbromide can be considered as a bromine-transfer agent. ... 

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